The efficiency of a wind turbine is in direct relation to the height of the rotor. There are obstacles in building higher support structure, also called wind towers, due to the limitation in cranes heights and transportability of the tower parts or the cranes.
Current cranes can lift up to heights of about 100 meters, the bottom (ground) diameter of a higher wind tower will be substantially be wider, meaning that the prefabricated cylindrical tower segments also would be larger, causing a lot of difficulties in transport and handling.
The industry tried to solve these problems by using different methods. Tubular towers made from cylindrical or tapered tube sections of rolled steel, flanged or welded on top each other were suggested. Prefabricated longitudinal tube sections mounted together axially to form a tubular tower are also suggested.
Another issue with generation of energy is that the electricity demand during a 24 h day cycle is very fluctuating, studies show that the peak periods are between 10:00 to 13:00 and from 18:00 to 20:00. The low period is between 3:00 and 5:00.
This is reflected in the cost per kWh. In peak moments it can be the double or triple of the low peak periods. FIG. 2 illustrate the average electricity cost at different moments in time.
The industry is working on different storage systems to store the electricity in low periods and making it available again during peak periods. For this they utilize for example pumped storage hydropower (PSH) or the CAES systems (Compressed Air Energy Systems).
Wind power is also facing the problem that in remote area (islands, deserts) where wind harvest could be very efficient the connection to the power grid is too costly and therefore not economically option.
To cope with these problems, the industry has so far presented the following methods:
W02011/008325 describes storage of compressed air in a wind turbine support structure. It discloses a method that utilizes the support structure of a wind turbine to store compressed air. Nevertheless, the support structure implies an enormous construction resulting in high complexity. The latter is rendered even more complex in view of the high pressures that are used in the system, being indicated as up to 300 bar, as indicated in the document. The structure described is referred to as a structure made of a (one) hollow tube wherein a compressed air chamber is contained within the walls of this tube structure. The tower structures are provided such that each tower has its own compressor. The complex process of erecting the support structure with integrated storage is not discussed.
W02011/032559 and W02009/097858 shows methods for erecting a tower structure using longitudinal tube segments. Such a method facilitates the transport of the tower elements, but it is rather complex to assemble all the required parts at the tower's building location. It also shows a method to erect a tower by lifting the individual tube segments into position using an internal hoisting device.
W02007/136765 shows a system for harvesting energy from wind where in the nacelle a compressor unit is installed instead of a generator. The use and production of compressed air is explained and methods are described to store the compressed gasses in natural or man-made vessels. The function of removing the heat coming from the compressors (cooling the compressor) and the possible advantages of pre-heating the compressed gas before it is expanded also is explained.
There is still a need for a system and method for storing gasses and for methods and systems for installing such storing systems.